Electrical measuring instrument.



No. 783,783. PATENTED FEB.,28', 1905. W. A. PRICE.

ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED FEB. 24. 1908.

2 SHEETS-SHEET 1 j 72 5 5141111586 58 /NV/V TOR MMW mm 102% No. 783,738.PATENTED FEB. 28, 1905. W. A. PRIGE. ELEGTEIGAL MEASURING INSTRUMENT.

APPLIUATION FILED FEB. 24. 1903.

2 SEEETS-BHEET 2.

No. 783,733. Patented February 28, I905.

NITED STATES PATENT I I ILEt WESTON A. PRICE, OF CLEVELAND, OHIO,ASSIGNOR TO THE ELECITRIC AND DENTAL SPECIALTY COMPANY, OF CLEVELAND,OIIIO, A COR- PORATION OF OHIO.

ELECTRICAL MEASURING INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 783,? 33, datedFebruary 28, 1905.

Application filed February 24, 1903. Serial No. 144,611.

TO 10/7/07 1:15 {l thereon in a suitable manner a casing or coverBeitknown thatLW'ns'roNA.Paton,aciti- B, which incloses substantialLyall of the 5 zen of the United States, and a resident of mechanismembodied in the lllStlLllilUllC. in Cleveland, county of Cuyahoga, andState of the central portion of this base and intersect- Ohio, haveinvented a new and useful Iming the upper surface thereof is formed adeprovement in Electrical Measuring Instrupression (t for receiving thelower member of ments, of which the following is a specificaa sectionalpermanent magnet C, which is setion,the principle of the invention beingherecured to the base by means of a plate c and a in explained and thebest mode in which I screw 0. Two concave polc'picces c" c" are to havecontemplated applying that principle, so secured upon the inner surfaceof the free as to distinguish it from other inventions. ends of themagnet, and upon the back of My invention relates to instruments forthese polepieces is secured, by means of measuringelectricalcurrents,andparticularly screws c, a su] )porting-piece 1;", formed with tomilliammeters used in dental cataphorcsis. a lug c, projecting betweenthe said two pole 5 The said inventionhas for its object the pro Ipieces, as shown in Figs. I and II. To the vision of an ammeter of suchdelicacy of coni inner surface of said lug is secured, by meansstruction and operation as will permit elecof a screw 0, a soft-ironcylindrical core C, trical currents of exceedingly small amperagecoaxial with the concave surface of the poleto effect a movement on thepart of the indipieces. The upper base of such core is inter- 20 eatingmeans connected therewith of comparasected by a centrally-locatedcylindrical bore tively large amplitude, so that readings of 0 fromwhich projects a needle-point 0, fixed thousandths of milliamperes,hundredths of to the core, as shown in Fig. Ill. Upon this milliamperes,tenths of milliamperes, millineedle-point is supported an armatureconamperes, as well as amperes, may be .made sisting of a coil I) ofinsulated wire wrapped 5 with facility and accuracy. upon a suitableframe (I. This frame has se' The said invention consists of meansherecured to it and projecting from the under inafter fully described,and particularly set surface of its upper portion a centrally-loforth inthe claims. cated bearing (Z, in which is journaled the The annexeddrawings and the following deneedle-point. It will hence be seen thatthe 3 scription set forth in detail certain mechancoil is mounted toswing freely in suspenism embodying the invention, such disclosed sionin the annular space between the polemeans constituting but one ofvarious mepieces and core, the needle -point forming 8O chanical formsin which the principle of the its sole support. Upon the upper surfaceof invention may be used. the pole-pieces are secured four headed pins35 In said annexed drawings, Figure I repree a, two on each pole-piece,Fig. I. These sents a plan view of a Inilliammeter embody pinsformabearing for an annular ring E, proing my invention, a part of thecasing or vided with arearwardly-projectinghandpiece 5 cover beingillustrated as broken away in ore, which projects through an aperture inthe der to disclose the mechanism. Fig. II repcover B. This aperture iscovered by a slid- 4- resents a vertical central longitudinal sectioning plate 0, provided with an opening for perof said milliamrneter,parts out by the plane mitting the passage therethrough of the handofsection being illustrated in elevation. Fig piece c, and is held inposition by a helical 9 III represents a vertical transverse sectionspring 0", mounted upon such handpiecc intaken upon the plane indicatedby the lines 3 termediately of said plate and the ring E, as

45 3 in Figs. I and II and viewed in the direcshown. Such plate in soclosing such opention indicated by the arrows in said figures. ingpermits of the partial rotation of the ring A base member A, preferablyof wood or and at the same time prevents dust, Sac, from othernon-conducting material, has secured entering the cover through opening6. Upon this ring E is secured an upright curved stud a, to the upperend of which is secured the outer end of a spiral retractable spring a,the inner end of which is secured to an axial pintle (Z secured to theframe (Z, Fig. III. The pins (1 c are placed so as to exert an amount offrictional contact upon ring E, such as will prevent same from havingits position unpremeditatedly altered after having been given a requiredposition. The lower end of the frame is provided with adownwardly-projecting axial pintle to which is secured the inner end ofa very sensitive spiral springe the outer end of which is secured to aclip f, secured to an insulated screw F, projecting from and secured tothe one pole-piece of the magnet, as shown in Fig. III. Said spring a isof a trend opposite that of spring 6*, the relaxation being therebyneutralized, and serves to steady and balance the coil. One end of thelatter is electrically connected with pintle (l and the other end withpintle cl", and the pole-pieces, ring E, stud c spring a, coil-pintle (Zcoil-spring 6, clip f, and screw F are all connected electrically inseries.

Two binding-posts G and H are provided and secured to the base A uponopposite sides of the cover B, as shown in Fig. I. Post Gr is connectedby a wire conductor g (shown in dotted lines in Fig. I) with the plate0. Post H is connected by a similar conductor it with the screw F. PostG is further connected by a second conductor g (shown in dotted lines inFig. I) with one end of a series of conductors J J J J J of varyingresistance. The other end of each such conductor is connected by meansof separate conductors f, and with one of a series of plug-seats 1, 2,8, 4t, and 5. A plug K is connected by means of a flexible conductor inwith the binding-post H.

The front of the coverB is downwardly inclined and provided with anopening 6 covered with glass. Behind such opening is secured a scale M,suitably divided and marked.

Secured to the upper portion of the coilframe (Z is anindicating-pointer L, the point of attachment lying, as shown,substantially in the plane intersecting the plane of theneedlepoint-that is, the point of support of the coil and parallel withthe direction of movement of the coil. Upon the side of the upper frameportion opposite that to which the pointer is secured is an adjustableweight Z, counterbalancing the weight of the pointer.

The above-described construction, owing to the presence of a minimumamount of frictional resistance on the part of the means supporting thecoil, is exceedingly sensitive to currents of extremely small amperage,so that a very considerable movement of the pointer is obtained byrelatively small variations in the current passing through the coil.

In operation the terminals of the line are secured to the binding-postsG and H and the current passes through the conductor 9,

plate 0, magnet O, ring E, stud 0 spring a", pintle (Z coil I), pintle(1, spring J, clip f, screw F, and so to the binding-post H. In practiceI use a scale about eight inches in length divided into fiftysubdivisions. A current of one-twentieth of a milliampere passingthrough the mechanism will effect a movement of eight inches on the partof the end of the pointer, so that a variation of one-thousandth of amilliampere will effect a movement of one-fiftieth of eight inches, oreightfiftieths of an inch, or approximately one-sixth of an inch.

When it is desired to measure a current of greater strength thanone-twentieth of a milliampere, the plug K is inserted in seat No. 1,and the variable resistance J so shunted into the circuit, the otherresistances being shunted into the circuit as is desired, the sizes ofsuch variable resistances being relatively decimal parts of each other.This resistance J illustrated I prefer to arrange so as to be one tonine as compared with the resistance of the mechanism. Under suchconditions but one-tenth of the current is effective and the readings onthe scale are taken in tenths and hundredths of milliamperes. Theinstrument is made ten times as sensitive as the above by means of sixplug-seats each connected with and similar to 7b, producing a scalemeasuring accurately a current of one-millionth of an ampere to tenamperes. In order to adjust the pointer so as to cause its end to restnormally upon Zero, the current is cut off, and the retractile force ofspring 6* is varied by turning the ring E, by means of the projectinghandpiece 0, until such desired position of the pointer is secured. Incase circumstances and conditions are such as to render the normalzero-point diflicult to see, the Zero-point may be moved by suchvariation of the force of the spring to an intermediate position on thescale so as to overcome such difficulty.

It is desirable when the instrument is not resting upon a fixed support,as when being carried about, to provide means for securing the coil, andhence the pointer, against move ment d uringsuch time. To this end Iprovide a plunger N, Fig. II, which is actuated to project or tend to beprojected from the bottom of the base a short distance by a helicalspring 92. The upper end of this plunger articulates with the end of alever at, whose other end carries a ring M, which is located immediatelybelow the frame (Z of the coil. The spring a is of such a strength thatthe weight of the instrument will effect its compression and depress thering a into the position shown in Fig. II. hen the instrument is liftedoff the support, said spring actuates the plunger to operate the lever nto raise the ring, cause it to engage the lower surface of the frame (Z,and effect contact between the latter and the core C. In such positionthe coil and pointer are held in a fixed position against vibration, sopreventing any possible injury to the bearing;

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the mechanismherein disclosed, provided the means stated by any one of the followingclaims or the equivalent of such stated means be employed.

ll therefore particularly point out and distinctly claim as myinvention- 1. In a measuring instrument, a suitable base, a magnetsupported there on,a coil mou nted and movable in the field of force ofsaid magnet,a n indicating-pointer secured thereto, means for steadyingsaid coil, means for moving the same independently of the variations olthe field of force, and means for securing the same against movementwhen the instrument is removed from a fixed support.

2. in a measuring instrument, a magnet, a conductor mounted and movablein the held of force of the same, a shunt-circuit comprising a pluralityof electrical resistances of varying values, means for shunting any orall of such resistances between the terminals of said. conductor, anindicating-pointer secured to the latter, a single bearing forsupporting said conductor, and means for lifting said. conductor, fromsaid bearing and securing it against movement when the instrument isremoved from a fixed support.

3. in a measuring instrument, the combination of a movable member andsuitable supporting means therefor, an inclosing casing, an indicatingpointer connected with said member, a retractile spring connected witheach end of the latter, the trend of one of said springs being oppositeto that of the other, a ring connected with one of said springs andnormally secured against rotation, and a suitable handpicee connected tosaid ring, projecting from said casing, and adapted upon its actuationto rotate said ring to vary the retractile strength of said spring.

i. In a measuring instrument, the combination of a base, a rotatablemember mounted thereon, an indicatingpointer secured to said member,means projected from the bottom of said base arranged to be actuated bythe weight of the instrument, and connected with said movable member insuch a manner as to secure the same against rotation upon being releasedfrom the weight 01 the instrument.

5. In a measuring instrument, the combination of a base, a rotatablemember mounted thereon and movable from off its bearing, an

indicating-pointer secured to said member, means projecting from thebottom of said base arranged to be actuated by the weight of theinstrument, said means being connected with said movable member in amanner such as when released from the weight of the instrument to liftsaid member from its bearing and secure it against rotation or movement.

6. In a measuring instrument,a base, a magnet, a conductor mounted andmovable in the [ield of force of the latter, a shunt-circuit comprisinga plurality of electrical resistances of varying values, means forshunting any or all of such resistances between the terminals of saidconductor, an indicating-pointer secured to the latter, a single bearingfor supporting said conductor, a plunger in the bottom of said base, aspring for actuating said, plunger out from said base when theinstrument is lifted from a lixed support, said spring being normallycompressed by the weight of the instrument, a lever actuated by theoutward movement of said plunger, and a ring actuated upwardly by themovement of said lever and adapted to contact with and lift saidconductor from its bearing and secure same against rotation or movement.

Signed by me this 10th day of February, 1903.

WESTON A. PRICE.

Attest:

Gr. W. SAYWELL, A. E. lVllGRKlQL.

